mm/z3fold.c: lock z3fold page before __SetPageMovable()

Following zsmalloc.c's example we call trylock_page() and unlock_page().
Also make z3fold_page_migrate() assert that newpage is passed in locked,
as per the documentation.

[akpm@linux-foundation.org: fix trylock_page return value test, per Shakeel]
Link: http://lkml.kernel.org/r/20190702005122.41036-1-henryburns@google.com
Link: http://lkml.kernel.org/r/20190702233538.52793-1-henryburns@google.com
Signed-off-by: Henry Burns <henryburns@google.com>
Suggested-by: Vitaly Wool <vitalywool@gmail.com>
Acked-by: Vitaly Wool <vitalywool@gmail.com>
Acked-by: David Rientjes <rientjes@google.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Vitaly Vul <vitaly.vul@sony.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Xidong Wang <wangxidong_97@163.com>
Cc: Jonathan Adams <jwadams@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/z3fold.c b/mm/z3fold.c
index 985732c8b025eb0c4064a18243114b25b34e5e87..dfcd69d08c1e9336d173657425b8017aadae5fb4 100644 (file)
--- a/mm/z3fold.c
+++ b/mm/z3fold.c
@@ -924,7 +924,16 @@ retry:
                set_bit(PAGE_HEADLESS, &page->private);
                goto headless;
        }
-       __SetPageMovable(page, pool->inode->i_mapping);
+       if (can_sleep) {
+               lock_page(page);
+               __SetPageMovable(page, pool->inode->i_mapping);
+               unlock_page(page);
+       } else {
+               if (trylock_page(page)) {
+                       __SetPageMovable(page, pool->inode->i_mapping);
+                       unlock_page(page);
+               }
+       }
        z3fold_page_lock(zhdr);
 
 found:
@@ -1331,6 +1340,7 @@ static int z3fold_page_migrate(struct address_space *mapping, struct page *newpa
 
        VM_BUG_ON_PAGE(!PageMovable(page), page);
        VM_BUG_ON_PAGE(!PageIsolated(page), page);
+       VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
 
        zhdr = page_address(page);
        pool = zhdr_to_pool(zhdr);